intro_to_pattern_languages.pdf

Pattern Languages For Interaction Design

by Victor Lombardi

| 0 4. 24.00 | report 15

a publication of th e science departme nt

…The language, and the processes which

stem from it, merely release the funda-

mental order which is native to us. They

do not teach us, they only remind us of

what we know already, and of what we

shall discover time and time again, when

we give up our ideas and opinions, and

do exactly what emerges from ourselves.

- Christopher Alexa n d e r, The Timeless Way of Building

tern, "Opening to the Street," is illustrated

with a photograph and begins with the

essence of the pattern: "The site of action

is an incentive for action. When people

can see into spaces from the street their

world is enlarged and made richer, there is

more understanding; and there is the pos -

sibility for communication, learning."

Notice his description focuses on the

human experience. Next is a detailed elab-

oration of this scenario, including a report

of his observations and other architectural

references. The pattern continues with a

solution: "In any public space which

depends for its success on its exposure to

the street, open it up, with a fully opening

wall which can be thrown wide open, and

if it is possible, include some part of the

activity on the far side of the pedestrian

path, so that it actually straddles the path,

and people walk through it as they walk

along the path…" He concludes the pat-

tern with a line drawing and a list of relat-

ed patterns.

user interface designers but actually

through the efforts of the programming

community. The method of documenting

invariant problems paired with their corre-

sponding solutions was a convenient way

to express repeating programming tech-

niques. Additionally, the concept of asso-

ciating these patterns in the hierarchical

structure of a pattern language translated

into interesting parallels for object-orient-

ed software design. The most notable

expression of design patterns in the soft-

ware field is the landmark book, Design

Patterns, by Gamma et al.

Introduction

In the late 1960s Christopher Alexander

and his associates embarked on a search

for a new method of architecture and

planning, studying how people interacted

with physical spaces. Several years later

they published a series of books describ-

ing this new method. With philosophy and

writing of soaring beauty, Alexander posits

that our lives consist mainly of patterns of

"A pattern language is

nothing more than a pre-

cise way of describing

someone's experience..."

-Christopher Alexander

"The pattern discipline

has become one of

the most widely

applied and important

ideas of the past

decade in software

architecture and

design." -James Coplien

James Coplien of Bell Laboratories com-

ments, "Focusing on objects had caused

us to lose the system perspective.

Preoccupation with design method had

caused us to lose the human perspective.

The curious parallels between Alexander’s

world of buildings and our world of soft-

ware construction helped the ideas to

take root and thrive in grassroots pro-

gramming communities worldwide. Th e

pattern discipline has become one of the

most widely applied and important ideas

of the past decade in software architec-

ture and design."

When writing his patterns, Alexander care-

fully selected the level of abstraction. The

patterns are concrete enough to use as

rules of thumb with good results, and yet

are sufficiently abstract to apply to count-

less situations, with an almost infinite vari-

ety of results.

A group of related design patterns are

referred to as a "pattern language." The

particular pattern language Alexa n d e r

wrote spans the entire scale of architec-

ture, from "Agricultural Valleys" to "Street

Cafes" to "Alcoves." But this language is

only one example; his hope is that every

living society and to some extent every

individual will identify their own pattern

language and use it to design their envi-

ronment.

events, and that architecture which sup-

ports these patterns helps us feel more

"alive" or "whole." He says, "A pattern lan-

guage is really nothing more than a pre-

cise way of describing someone’s experi-

ence of a building." This approach of

focusing on people relates directly to the

Razorfish philosophy of creating user

experiences.

The software community started a series

of Pattern Languages of Programming

conferences to further creation and use of

design patterns. It was in these confer-

ences that design patterns were first cre-

ated for interaction design.

Pattern Languages

in Computer Science

The concept of pattern languages crossed

over to the computer science field not via

Pattern Languages

for Interaction Design

There is a small, active community of inter-

action designers around the world cur-

Alexander recorded his observations in a

format called "design patterns" which

summarize the context of a problem and

its solution. For example, one design pat-

Pattern Languages for Interaction Design

rently creating design patterns and exper-

imenting with their use. An example is

Common Ground, a user interface pattern

language created by Jenifer Tidwell at the

M a s sa chusetts Institute of Te ch n o l o g y.

Here is a summary of one of her patterns:

Pointer Shows Affordance

Examples:

• Finger pointer over a hyperlink, especially

pictorial links

• Buttons whose borders change when

you point to them

tion enables designers to use this design

pattern repeatedly while never duplicating

the details of implementation.

ing, by helping designers form educated

design choices at the beginning of a project.

The Challenge

At the Object-Oriented Programs,

Systems, Languages, and Applications

conference in 1996, Christopher

Alexander lamented that architects still do

not create in a generative way through

observation of human experience. He

pointed out that the spread of computers

effectively increases the influence of com-

puter professionals in a way that could

prove more important to human experi-

ence than architecture. He ch a l l e n g e d

software professionals to create the "nat-

ural, genetic infrastructure of a living world

which you/we are capable of creating,

managing, making available, and which

could then have the result that a living

structure…becomes an attainable thing."

"Focusing on objects

had caused us to

lose the system per-

spective.

Preoccupation with

design method had

caused us to lose the

human perspective."

-James Coplien

Context: The artifact contains a pointer, or

"virtual fingertip" (mouse or pen point, for

instance) that is the focal point for the

user’s interaction with the artifact…

Problem: How can the artifact indicate

that an entity represents an action that the

user may take?

Benefits

Interest in pattern languages for computer

interaction design continues to grow for

several reasons. First, design patterns pro-

vide an accessible format to document

design knowledge on a personal, project,

or organizational level, creating a com-

plete but accessible reference source.

Design patterns elegantly summarize a

problem, context, examples, and solution

in a format that is more rigorous than a

heuristic and more accessible than a

library of design books.

Forces: Static affordances aren’t always

enough to indicate the presence of a

m a n i p u l a table control, especially when

space is tight or when an esthetic design

is of paramount importance.

for more information

Alexander, Christopher.

The Timeless Way of Building. Oxford

University Press, 1979.

Solution: Change the affordance of the

thing as the pointer moves over it. This can

be done by changing the pointer to com-

municate what action can be performed or

by changing the artifact to make it stand

out perceptually…

Alexander, Christopher.

A Pattern Language: Towns, Building,

Construction. Oxford University Press,1977.

Second, the format of design patterns

facilitates communication with other par-

ticipants of a design project. Because

design is a distributed social process,

effective communication plays an impor-

tant role.

Alexander, Christopher.

The Origins of Pattern Theory: The Future

of the Theory, and the Generation of a

Living World.

http://www.computer.org/software/

so1999/s5071abs.htm

Tidwell concludes this pattern with the

resulting context, an illustration, refer-

ences to related patterns in her language,

and examples of well-known interface

designs. This pattern contributes to a pat-

tern language spanning all of user inter-

face design, including patterns such as

"Background Posture," "Status Display,"

and "Progress Indicator."

Erickson, Thomas.

The Interaction Design Patterns Page.

http://www.pliant.org/personal/

Tom_Erickson/InteractionPatterns.html

Third, pattern languages serve as a tool to

practice actual design. They move the

designer to an abstract level to help

escape repetition and encourage innova-

tion. Because design patterns transcend

particular implementations, they assist the

designer in moving easily among plat-

forms, devices, and media (visual, audito-

ry, haptic, etc.). When used as a toolbox of

t e chniques, design patterns can lower

costs, in terms of time and usability test-

Gamma, Erich, et al.

Design Patterns: Elements of Reusable

Object-Oriented Software .

Addison-Wesley, 1995.

This pattern language shows consistency

with Alexander’s ideas in several ways: the

focus on human interaction, the format

that includes a problem, context, and solu-

tion, and the composition of a language

describing human behavior within an envi -

ronment. Additionally, the level of abstrac-

Tidwell, Jenifer.

Common Ground: A Pattern Language

for Human-Computer Interface Design.

http://www.mit.edu/~jtidwell/

interaction_patterns.html

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